This invention relates to a device for minimizing the clearance between blade tips and surrounding shroud. In this art, many different types of shroud have been used. A sample of these are shown by U.S. Pat. Nos. 3,391,904; 2,859,934; 3,443,791 and 3,742,705. Turbine blade tip clearance is difficult to control because blade tip growth is made up of two elements that are different in thermal response rate; the blade responds rapidly while the disk responds more slowly. Presently, attempts are made to control blade tip clearance by trying to duplicate blade tip growth with a third element.